title: A longitudinal study of plasma and urinary cortisol in pregnancy and postpartum.
abstract: BACKGROUND
  There is a paucity of longitudinal data on plasma and urinary cortisol levels during pregnancy using modern assays. Furthermore, conflicting data exist as to the effect of the low-dose oral contraceptive pill (OCP) on cortisol. DESIGN, SUBJECTS, AND MEASUREMENTS: We conducted a prospective longitudinal study on morning plasma cortisol (total and free), corticosteroid-binding globulin (CBG), and 24-h urinary free cortisol (UFC) levels in 20 pregnant women during the first, second, and third trimesters and 2-3 months postpartum compared with 12 subjects on low-dose OCP and 15 nonpregnant subjects not taking the OCP (control group).
  
  
  RESULTS
  A progressive rise in total plasma cortisol, CBG, and 24-h UFC was demonstrated during pregnancy, peaking during the third trimester (mean 3-fold rise compared with controls). Plasma free cortisol increased 1.6-fold by the third trimester. In the OCP group, total plasma cortisol and CBG were 2.9- and 2.6-fold elevated, respectively, whereas 24-h UFC and plasma free cortisol were not significantly different from controls. Compared with liquid chromatography-mass spectrometry, a commercial immunoassay underestimated mean total plasma cortisol concentrations by 30% during second and third trimesters and in OCP users and overestimated UFC levels by 30-35% during pregnancy.
  
  
  CONCLUSIONS
  Our study demonstrated elevations in total plasma cortisol and CBG concentrations during pregnancy and with low-dose OCP use. Pregnancy was also associated with significant increases in plasma free cortisol and UFC, suggesting that the rise in total plasma cortisol is contributed to by up-regulation of the maternal hypothalamic-pituitary-adrenal axis in addition to elevated CBG.
authors.affiliation: Department of Endocrinology, St. Vincent's Hospital, Melbourne, Melbourne, Victoria 3065, Australia. caroline.jung@svhm.org.au
authors.forename: Caroline
authors.initials: C
authors.lastname: Jung
authors.forename: Jui T
authors.initials: JT
authors.lastname: Ho
authors.forename: David J
authors.initials: DJ
authors.lastname: Torpy
authors.forename: Anne
authors.initials: A
authors.lastname: Rogers
authors.forename: Matt
authors.initials: M
authors.lastname: Doogue
authors.forename: John G
authors.initials: JG
authors.lastname: Lewis
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Czajko
authors.forename: Warrick J
authors.initials: WJ
authors.lastname: Inder
mesh_terms: D000328:Adult; D015992:Body Mass Index; D002851:Chromatography, High Pressure Liquid; D003278:Contraceptives, Oral, Hormonal / Q000009:adverse effects; D003348:Cortisone / Q000097:blood; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood* / Q000652:urine*; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D007118:Immunoassay; D008137:Longitudinal Studies; D010913:Pituitary-Adrenal System / Q000502:physiology; D049590:Postpartum Period / Q000097:blood* / Q000652:urine*; D011247:Pregnancy; D011263:Pregnancy Trimester, Third / Q000097:blood; D011446:Prospective Studies; D053719:Tandem Mass Spectrometry; D014156:Transcortin / Q000378:metabolism
chemical_list: D003278:Contraceptives, Oral, Hormonal; D014156:Transcortin; D003348:Cortisone; D006854:Hydrocortisone